Biology Biomolecules AJK 2019
PMDC Verified Question 124 of 142
The head of phospholipid molecule is polar (hydrophilic) due to:
A
Fatty acid
B
Phosphate
C
Carboxylic acid
D
Triacylglycerol
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Phosphate
Concept:

Phospholipids are amphipathic molecules, meaning they possess both a water-loving head and water-fearing tails.

Solution:

  • A phospholipid consists of a glycerol backbone attached to two non-polar fatty acid tails and one strongly polar head group.


  • This head group derives its intense polarity and negative electrical charge from the Phosphate group (\(PO_4^{3-}\)).


  • Because the phosphate is charged, it readily forms electrostatic interactions and hydrogen bonds with water, making the "head" completely hydrophilic.


Why other options are incorrect:

  • Fatty acids: Form the long, highly non-polar, hydrophobic tails.


  • Carboxylic acid: These groups on the fatty acids are lost (converted to ester bonds) during synthesis, so they don't contribute to head polarity.


  • Triacylglycerol: A completely different, fully non-polar storage fat molecule that lacks a phosphate entirely.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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